RELATED APPLICATIONS
STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH OR DEVELOPMENT
BACKGROUND ART
[0003] Use of magnesium citrate and magnesium bis-glycinates salt, either independently
or blended, often yield attributes or performance that is less than desirable. Magnesium
citrate tribasic exhibits poor aqueous solubility and can be difficult to compress
in tableting applications due to low compressibility. Magnesium bis-glycinate has
decent aqueous solubility, however, magnesium bis-glycinate salts also exhibit poor
compression indices and have a very unpleasant taste profile which can limit their
use in foods, beverages, and other oral applications.
[0004] US2005/220865 discloses a composition which provides rapid dissolution of magnesium salt. Both
magnesium glycinate and magnesium citrate are listed as possible sources of magnesium.
SUMMARY OF THE INVENTION
[0005] A novel concept has been developed in magnesium citrate glycinate co-salt which incorporates
an equal molar ratio of citric acid and glycine, completely neutralized with magnesium
in a metal to ligand ratio of 2:1:1 (i.e., 2 moles Mg, 1 mole citrate and 1 mole glycinate).
This new co-salt mitigates issues regarding poor compressibility and low magnesium
loading and improves aqueous solubility and poor organoleptic properties associated
with the use of magnesium citrate and magnesium bis-glycinate salts either independently
or as blends thereof.
[0006] Briefly, the magnesium citrate glycinate co-salt having a formula of Mg
2C
8H
9NO
9 - X H
2O and a suggested structure of:

[0007] The magnesium citrate glycinate co-salt has an apparent density of 1740 kg/m3.
[0008] The magnesium citrate glycinate co-salt is compressible in a range of compression
pressures from approximately 50 MPa to approximately 150 MPa.
[0009] The magnesium citrate glycinate co-salt is prepared by combining citric acid and
glycine in a 1:1 molar ratio to form an aqueous reaction mixture of citric acid and
glycine solution and then neutralizing the aqueous reaction mixture with a magnesium
source having a magnesium- ligand ratio of 1:1.
[0010] The magnesium source can be magnesium, a magnesium oxide, a magnesium hydroxide,
or a magnesium carbonate. The reaction mechanism for producing the co-salt being:
2Mg + C
6H
8O
7 + C
2H
5NO
2 → Mg
2C
8H
9NO
9(aq) + 4 H
2(g)
-or-
2MgO + C
6H
8O
7 + C
2H
5NO
2 4 Mg
2C
8H
9NO
9(aq) + 2 H
2O
(I)
-or-
2Mg(OH)
2 + C
6H
8O
7 + C
2H
5NO
2 4 Mg
2C
8H
9NO
9(aq) + 4 H
2O
(I)
-or-
2MgCO
3 + C
6H
8O
7 + C
2H
5NO
2 4 Mg
2C
8H
9NO
9(aq) + 2 H
2O
(I) + 2 CO
2(g)
[0011] The neutralization step includes neutralizing the 1:1 molar ratio of citric acid
and glycine aqueous solution to a pH between 8.5 - 10.5 to form a neutralized solution.
[0012] The neutralized solution can then be dried to a free-flowing powder.
[0013] To demonstrate the unique nature of the magnesium citrate glycinate co-salt, attempts
to produce other divalent metal to ligand ratio 2:1:1 co-salts were unsuccessful.
These divalent metals include calcium, copper, and zinc in which the insoluble divalent
metal tribasic citrate salt is precipitated when the reaction pH is taken through
the 2
nd pKa of citric acid (pH = 4.8), leaving the glycine solubilized in the mother liquors.
Experiments using iron and manganese were also unsuccessful due to rapid oxidation
of the metals in the reaction mass when approaching the pH needed to completely neutralize
the acid solution. These reactions were obviously terminated due to the non-divalent
nature of the products being produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
FIGS. 1-3 show Thermogravimetric Analysis (TGA) patterns for magnesium bis-glycinate,
magnesium citrate tribasic, and a "component dry blend" of magnesium bis-glycinate
and magnesium citrate tribasic;
FIG. 4 shows the TGA pattern for a magnesium citrate glycinate co-salt sample;
FIGS. 5-7 show the FT-IR spectra for magnesium bis-glycinate magnesium citrate tribasic,
and the "component dry blend", respectively;
FIG. 8 shows the FT-IR spectrum for the magnesium citrate glycinate co-salt sample;
FIGS. 9-11 show SEM (Scanning Electron Microscopy) imaging of magnesium bis-glycinate,
magnesium citrate tribasic and magnesium citrate glycinate co-salt, respectively;
FIGS. 12-14 show XRD patterns for magnesium bis-glycinate, magnesium citrate tribasic,
and the "dry blend", respectively;
FIG. 15 shows the XRD pattern for the magnesium citrate glycinate co-salt sample;
FIGS. 16-18 show the XRD patterns for failed attempts to produce calcium citrate glycinate,
copper citrate glycinate and zinc citrate glycinate, respectively;
FIG. 19 is a photograph of magnesium citrate glycinate co-salt (left) and the "Component
Dry Blend (right);
FIG 20 is a photograph of magnesium citrate glycinate co-salt (left) and "Component
Dry Blend (right) each in water;
FIG. 21 is a photograph of magnesium citrate glycinate co-salt (left) after 24 hours
in water;
FIG. 22 is a graph of particle size distribution of the magnesium citrate glycinate
co-salt sample;
FIG. 23 contains compression profiles of the magnesium citrate glycinate co-salt sample;
[0015] Corresponding reference numerals will be used throughout the several figures of the
drawings.
DETAILED DESCRIPTION
[0016] The following detailed description illustrates the claimed invention by way of example
and not by way of limitation. This description will clearly enable one skilled in
the art to make and use the claimed invention, and describes several embodiments,
adaptations, variations, alternatives and uses of the claimed invention, including
what we presently believe is the best mode of carrying out the claimed invention.
Additionally, it is to be understood that the claimed invention is not limited in
its application to the details of construction and the arrangements of components
set forth in the following description or illustrated in the drawings. The claimed
invention is capable of other embodiments and of being practiced or being carried
out in various ways. Also, it is to be understood that the phraseology and terminology
used herein is for the purpose of description and should not be regarded as limiting.
[0017] Several laboratory samples of magnesium citrate glycinate co-salt were prepared for
use in demonstrating both matter of composition and comparative studies against both
magnesium citrate tribasic and magnesium bis-glycinate.
[0018] Magnesium citrate glycinate co-salt when prepared correctly has a molecular formula
of Mg
2C
8H
9NO
9 - X H
2O as shown in production of an aqueous solution in
Equation 1 and by drying to a free-flowing powder in
Equation 2.
Equation 1: 2 MgO + C
6H
8O
7(aq) + C
2H
5NO
2(aq) → Mg
2C
8H
9NO
9(aq) + 2 H
2O
(I)
Equation 2: Mg
2C
8H
9NO
9(aq) → Mg
2C
8H
9NO
9 - X H
2O (Drying Step)
[0019] It is believed that the magnesium citrate glycinate co-salt has the following structure:

[0020] The source for the magnesium can be magnesium oxide (as shown above in Equation 1).
Alternatively, the magnesium source can be magnesium, a magnesium hydroxide or carbonate
(i.e., Mg, Mg(OH)
2 or MgCOs). In this case, Equation 1 would be shown be Equation 1b-1d below:
Equation 1b: 2Mg + C
6H
8O
7 + C
2H
5NO
2 → Mg
2C
8H
9NO
9(aq) + 4 H
2(g)
Equation 1c: 2 Mg(OH)
2 + C
6H
8O
7 + C
2H
5NO
2 → Mg
2C
8H
9NO
9(aq) + 4H
2O
(I)
Equation 1d: 2 MgCOs + C
6H
8O
7 + C
2H
5NO
2 → Mg
2C
8H
9NO
9(aq) + 2 H
2O
(I) + CO
2(g)
[0021] Magnesium citrate glycinate co-salt has a molecular weight of 311.8 g/mol and magnesium
content of 15.6% on an anhydrous basis. The co-salt typically is found to contain
between 0.0 - 20.0% water depending on extent of drying.
[0022] To demonstrate matter of composition and product superiority, classical chemistry
methodology (assay), thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR),
X-ray diffraction (XRD), aqueous solubility and organoleptic (taste) testing were
implemented.
[0023] To assist in matter of composition and comparison, a dry blend was prepared by mixing
1/2 mole of magnesium citrate tribasic hydrate with 1/2 mole of magnesium bis-glycinate.
This dry blend possesses the same 1:1 metal to ligand molar ratio as does di-magnesium
citrate glycinate (2 moles Mg, 1 mole citrate and 1 mole glycinate). This sample will
further be referred to as the
"component dry blend" and will be used to help demonstrate the novel magnesium citrate glycinate co-salt's
composition uniqueness and superiority to individual magnesium citrate tribasic and
magnesium bis-glycinate.
Classical Chemistry Methodology
[0024] Research samples of magnesium citrate glycinate co-salts (Samples A and B) and pilot
scale sample (Sample C) were prepared and analyzed for magnesium content using EDTA
titration. The water content of both samples was determined by TGA so that the anhydrous
magnesium content could be calculated and compared to theoretical anhydrous magnesium
content. The three samples shown in
Table 1 all contain the precise theoretical amount of magnesium that is consistent with the
di-magnesium citrate glycinate co-salt formula.
Table 1:
| Magnesium Content Water Content and Theoretical Assay values for Magnesium Citrate
Glycinate Co-salts |
| Sample |
% Mg (as is) |
% Water |
% Mg Anhydrous |
% of Theoretical Mg (15.6%) |
| A |
13.1% |
16.1% |
15.6% |
100.0% |
| B |
12.6% |
19.5% |
15.7% |
100.6% |
| C |
13.2% |
15.7% |
15.7% |
100.6% |
Thermoaravimetric Analysis (TGA)
[0025] TGA was used not only to accurately determine the water content of the co-salts being
produced as shown in
Table 1 but was also employed to demonstrate the uniqueness of the co-salt against magnesium
citrate tribasic, magnesium bis-glycinate and the "component dry blend" described
in the Invention Description.
Figures 1-3 show the TGA pattern for magnesium bis-glycinate, magnesium citrate tribasic, and
the "component dry blend".
[0026] One can clearly see in
Figures 1 and 2 that the TGA patterns for magnesium bis-glycinate and magnesium citrate tribasic
are highly ordered and indicative of waters of crystallization being released over
a small range of temperature demonstrated by the steep slope of the weight (%) signal.
The TGA of the "component dry blend" in
Figure 3 also shows this type of water loss pattern. Those skilled in the art will also recognize
that the "component dry blend" TGA shows both magnesium citrate tribasic and magnesium
bis-glycinate weight loss events.
[0027] Figure 4 shows the TGA pattern for a magnesium citrate glycinate co-salt sample prepared according
to the method of Example 1 (below). Clearly, this pattern is different than the patterns
seen in
Figures 1-3, as the weight loss event is happening over a very broad temperature range. These
types of TGA patterns are indicative of amorphous solids.
[0028] If the co-salt sample were merely a co-precipitation of magnesium citrate and magnesium
bis-glycinate, the TGA pattern would look identical to
Figure 3. However, this co-salt technology is not a co-precipitated product of separate magnesium
citrate and bis-glycinate components, but a unique chemical entity as demonstrated
by comparing
Figures 3 and 4. That is, the TGA pattern indicates that the product is not a mere mixture of magnesium
citrate and bis-glycinate, but rather, a unique compound.
FT-IR Spectroscopy
[0029] Infrared spectroscopy was also employed to demonstrate the uniqueness of the co-salt
against magnesium citrate tribasic, magnesium bis-glycinate and the "component dry
blend" described in the Invention Description.
Figures 5-7 show the FT-IR spectra for magnesium bis-glycinate magnesium citrate tribasic, and
the "component dry blend".
[0030] Magnesium Bis-glycinate
(Figure 5) shows strong absorbances in the fingerprint region of 1572, 1404, 1319, 1107 and
1036 cm
-1 and a distribution of strong absorbances between approximately 630 and 820 cm
-1.
[0031] Magnesium Citrate Tribasic (
Figure 6) has strong absorbances in the fingerprint region of 1573, 1413, 1271 and 1140 cm
-1 and a distribution of weaker less defined absorbances between approximately 391 and
634 cm
-1
[0032] The "Component Dry Blend" (
Figure 7) has strong absorbances in the fingerprint region of 1587, 1413, 1271 and 1136 cm
-1. Looking closer at its strong absorptions and peak shapes, one skilled in the art
would discern that this is indeed a physical blend as both aspects of the independent
spectra (
Figures 5 and 6) are visible yet muted by each other.
[0033] The Ft-IR spectrum for magnesium citrate glycinate co-salt (Sample A) is shown in
Figure 8. The co-salt has strong absorbances in the fingerprint region of 1566 and 1400 cm
-1. Take note that the sharp absorbances between 750- 1350 cm
-1 found in
Figures 5-7 are either gone or have been substantially broadened.
[0034] The FT-IR spectra of the "component dry blend" in
Figure 7 and the magnesium citrate glycinate co-salt in
Figure 8 are substantially different, providing strong evidence that the co-salt is a unique
entity or compound and not a mere blend or mixture of magnesium citrate and bis-glycinate
components.
Particle Morphology by Scanning Electron Microscopy
[0035] The unique nature of the magnesium citrate glycinate co-salt can be both demonstrated
and differentiated form magnesium citrate tribasic and magnesium glycinate.
Figures 9-11 show SEM (Scanning Electron Microscopy) imaging of magnesium bis-glycinate, magnesium
citrate tribasic and magnesium citrate glycinate co-salt respectively.
[0036] As shown in
Figure 9, magnesium bis-glycinate has a polycrystalline presentation, composed of many crystallites
of varying size and orientation. SEM imaging of magnesium citrate tribasic shown in
Figure 10 shows a singular type of crystallinity dictated by layers of mono/triclinic plates.
[0037] SEM imagery of magnesium citrate glycinate co-salt shown in
Figure 11 demonstrates the amorphous nature of this product. Lack of either the polycrystalline
crystallites found in magnesium bis-glycinate or triclinic plates found in magnesium
citrate tribasic demonstrate that this co-salt is not a mere co-precipitated blend
of magnesium citrate and magnesium bis-glycinate, but a unique chemical entity or
compound.
X-Ray Diffraction (XRD) Pattern Analysis
[0038] As described in Thermogravimetric Analysis and Particle Morphology by Scanning Electron
Microscopy, magnesium bis-glycinate and magnesium citrate tribasic are relatively
high crystalline materials and as such have very distinct and reproducible XRD patterns
which are shown in
Figures 12 and 13.
[0039] Likewise, the "component dry blend" described above displays distinct XRD patterns
consistent with both magnesium bis-glycinate and magnesium citrate tribasic as shown
in
Figure 14.
[0040] Due to the amorphous nature of magnesium citrate glycinate co-salt as described in
Particle Morphology by Scanning Electron Microscopy, this compound does not show any
degree of crystallinity by XRD as shown in
Figure 15.
[0041] The fact that the "component dry blend" shows both magnesium bis-glycinate and magnesium
citrate tribasic theta signals and the magnesium citrate glycinate co-salt does not,
provides strong evidence that the co-salt is a unique entity (compound) and not a
mere blend of components.
Aqueous Solubility
[0042] Magnesium glycinate is known to possess good aqueous solubility while magnesium citrate
does not. Magnesium citrate glycinate co-salt exhibits excellent aqueous solubility
unlike the "component dry blend" described above. To demonstrate, 10g of magnesium
citrate glycinate co-salt and 10g of the "component dry blend" (
FIG. 19) were simultaneously each added to 90 g DI water at room temperature. Once stirring
was initiated, the magnesium citrate glycinate co-salt sample almost instantly went
into solution while the "component dry blend" sample was an insoluble slurry (
FIG. 20). After 5 minutes of stirring, the magnesium citrate glycinate co-salt sample had
affected a clear and colorless solution while the "component dry blend" sample remained
a slurry.
[0043] The clear and colorless 10% w/w solution of magnesium citrate glycinate co-salt was
allowed to sit for 24 hours. Inspection (
FIG. 21) of the co-salt sample solution yielded no change in the clear and colorless moniker
put on the initial solution thereby demonstrating the aqueous stability of the magnesium
citrate glycinate co-salt
Compressibility
[0044] Compressibility of a second sample of magnesium citrate glycinate was evaluated using
an instrumented Carver press. Approximately 1.6 g, 5 mm thick tablets were compressed
using the 0.4"x0.9" rectangular tooling. No excipients were used. The sides of the
tooling were slightly dusted with magnesium stearate in order to facilitate tablet
ejection and eliminate sticking. The tablets were subjected to a three-point bend
stress using a TA.XT2-Plus texture analyzer (from Stable Micro Systems of Surrey,
England). Flexural strength and young modulus of the compact were measured. In addition,
compact density was calculated from the weight and size measurements of the tablets.
[0045] An attempt was made to compare compressibility of magnesium citrate glycinate with
those of individual salts, magnesium citrate tribasic and magnesium bis-glycinate.
However, these materials were characterized by inadequate compressibility and no cohesive
tablets were obtained under the current experimental conditions.
[0046] In addition, particle size distribution and apparent density of di-magnesium citrate
glycinate co-salt were measured. Particle size distribution of the second sample of
di-magnesium citrate glycinate is shown in
Figure 22.
[0047] Magnesium citrate glycinate co-salt is characterized by apparent density of 1740
kg/m
3.
[0048] Compression profiles of the tablets are shown in the
Figure 23.
[0049] At the higher pressures the product is over-compressed, however magnesium citrate
glycinate co-salt is compressible in the range of compression pressures from approximately
50 MPa to approximately 150 MPa. The individual citrate and glycine salts failed to
tablet as mention earlier.
Organoleptic Properties
[0050] Bis-Glycinate salts generally taste rather unfavorably and often are used in conjunction
with flavor masking agents to achieve a palatable end product. An internal taste testing
panel has confirmed that the taste profile of the magnesium citrate glycinate co-salt
is far superior to the individual magnesium bis-glycinate.
Examples:
[0051] The first two examples demonstrate the preparation of the magnesium citrate glycinate
co-salt.
Example 1: Lab Scale Preparation of Magnesium Citrate Glycinate Co-Salt.
[0052] An aqueous reaction mixture was prepared comprising 96.2g anhydrous citric acid and
37.5g glycine dissolved in 1000g of water. The aqueous reaction mixture was heated
to between about 60°C - 80°C. The resulting acid solution was neutralized with 40.3g
of magnesium oxide and adjusted to a pH between about 8.5-10.5 during a 4-8-hour digestion
between about 60°C - 80°C. Once the pH had stabilized, the resulting reaction mass
contained 155.9g of magnesium citrate glycinate co-salt having a metal to ligand ratio
of 1:1 remaining in solution. The reaction mass was filtered to remove any unreacted
magnesium oxide and other extraneous matter. The filtrate was dried to produce a free-flowing
powder containing magnesium citrate glycinate co-salt having a metal to ligand ratio
of 1:1 and a moisture content of between 0.0 - 20.0%.
Example 2: Pilot Plant Scale Preparation of Magnesium Citrate Glycinate Co-Salt.
[0053] An aqueous reaction mixture was prepared comprising 2.41Kg anhydrous citric acid
and 0.94Kg glycine dissolved in 25Kg of water. The mixture was heated to between about
60°C - 80°C. The resulting acid solution was neutralized with 1.1Kg of magnesium oxide
and adjusted to a pH between about 8.5-10.5 during a 4-8-hour digestion at about 60°C
- 80°C. Once the pH had stabilized, the resulting reaction mass contained 3.90Kg of
magnesium citrate glycinate co-salt having a metal to ligand ratio of 1:1 remaining
in solution. The reaction mass was filtered to remove any unreacted magnesium oxide
and other extraneous matter. The filtrate was dried to produce a free-flowing powder
containing magnesium citrate glycinate co-salt having a metal to ligand ratio of 1:1
and a moisture content of 0.0 - 20.0%.
[0054] It was initially thought that the same process could be used to prepare similar co-salts
with other di-valent metals, such as zinc, calcium, iron (ferrous), strontium, chromium,
copper, nickel, manganese, and molybdenum. However, as shown in the Examples 3-7 below,
attempts to produce calcium, copper, zinc, ferrous, and manganese citrate glycinate
co-salts did not work. These salts will, if producible, will need to be produced by
another route.
Example 3: Lab Scale Preparation of Calcium Citrate Glycinate Co-Salt.
[0055] An aqueous reaction mixture was prepared comprising 96.2g anhydrous citric acid and
37.5g glycine dissolved in 1000g of water. The mixture was heated to about 60°C -
80°C. The resulting acid solution was neutralized with 74.1g of calcium hydroxide
and adjusted to a pH between 8.5-10.5 during a 4-8-hour digestion at about 60°C -
80°C. Once the pH had risen above approximately 4.8, the reaction mass produced copious
white precipitate. The reaction mass was filtered to isolate the precipitate. The
precipitate was dried to produce a free-flowing powder containing only calcium citrate,
shown by XRD (see Fig. 16). The desired calcium citrate glycinate co-salt was not
produced.
Example 4: Lab Scale Preparation of Copper Citrate Glycinate Co-Salt.
[0056] An aqueous reaction mixture was prepared comprising 96.2g anhydrous citric acid and
37.5g glycine dissolved in 1000g of water. The mixture was heated to about 60°C -
80°C. The resulting acid solution was neutralized with 110.6g of basic copper carbonate
and adjusted to a pH between 8.5-10.5 during a 4-8-hour digestion at about 60°C -
80°C. Once the pH had risen above approximately 4.8, the reaction mass produced copious
blue/green precipitate. The reaction mass was filtered to isolate the precipitate.
The precipitate was dried to produce a free-flowing powder containing only copper
citrate, shown by XRD (see Fig. 17). The desired copper citrate glycinate co-salt
was not produced.
Example 5: Lab Scale Preparation of Zinc Citrate Glycinate Co-Salt.
[0057] An aqueous reaction mixture was prepared comprising 96.2g anhydrous citric acid and
37.5g glycine dissolved in 1000g of water. The mixture was heated to about 60°C -
80°C. The resulting acid solution was neutralized with 81.4g of zinc oxide and adjusted
to a pH between 8.5-10.5 during a 4-8-hour digestion at about 60°C - 80°C. Once the
pH had risen above approximately 4.8, the reaction mass produced copious white precipitate.
The reaction mass was filtered to isolate the precipitate. The precipitate was dried
to produce a free-flowing powder containing only zinc citrate, shown by XRD (see Fig.
18). The desired zinc citrate glycinate co-salt was not produced.
Example 6: Lab Scale Preparation of Ferrous Citrate Glycinate Co-Salt.
[0058] An aqueous reaction mixture was prepared comprising 96.2g anhydrous citric acid and
37.5g glycine dissolved in 1000g of water. The mixture was heated to about 60°C -
80°C. The resulting acid solution was neutralized with 55.85g of iron powder and adjusted
to a pH between 8.5-10.5 during a 4-8-hour digestion at about 60°C - 80°C. Once the
pH had risen above approximately 7.0, the reaction mass darkened significantly, as
the iron(II) was oxidized to iron (III). The reaction was terminated as the desired
ferrous citrate glycinate would not be produced at 100% purity due to oxidation of
the iron.
Example 7: Lab Scale Preparation of Manganese Citrate Glycinate Co-Salt.
[0059] An aqueous reaction mixture was prepared comprising 96.2g anhydrous citric acid and
37.5g glycine dissolved in 1000g of water. The mixture was heated to about 60°C -
80°C. The resulting acid solution was neutralized with 54.9g of manganese powder and
adjusted to a pH between 8.5-10.5 during a 4-8-hour digestion at about 60°C - 80°C.
Once the pH had risen above approximately 6.0, the reaction mass darkened significantly,
as the manganese(II) was oxidizing and producing insoluble manganese dioxide precipitate.
The reaction was terminated as the desired divalent manganese citrate glycinate would
not be produced at 100% purity due to oxidation of the manganese.
[0060] In view of the above, it will be seen that the several objects and advantages of
the present invention have been achieved and other advantageous results have been
obtained.
[0061] As various changes could be made in the above constructions without departing from
the scope of the invention, it is intended that all matter contained in the above
description or shown in the accompanying drawings shall be interpreted as illustrative
and not in a limiting sense.